The CCGS Hudson cruise Hud2007045 was the 2007 fall cruise of the Canadian Atlantic Zone Monitoring Program (AZMP, http://www.meds-sdmm.dfo-mpo.gc.ca/zmp/main_zmp_e.html). During the cruise, several Canadian and UK mooring stations on the Scotian Slope were visited and instruments were recovered and redeployed. CTD casts at the stations, as well as various biogeochemical measurements and sampling, were also carried out. The British crew for this cruise was made of technicians and scientists from the Proudman Oceanographic Laboratory (POL) and the National Oceanography Centre Southampton (NOCS): two BPR technicians (P. Foden and J. Pugh, POL), two mooring technicians from NOCS (J. Wynar and D. Comben, NOCS) and a PI (M. Maqueda, POL).

From an UK perspective, Hud2007045 was the fifth field campaign of the project RAPID-WAVE (West Atlantic Variability Experiment). RAPID-WAVE is funded by the UK Natural Environment Research Council (NERC) through the thematic programme "Rapid Climate Change (RAPID)". The project leaders are Chris Hughes (Proudman Oceanographic Laboratory), Richard Williams (University of Liverpool) and David Marshall (University of Reading). John Toole (Woods Hole Oceanographic Institution, WHOI) and John Loder (Bedford Institute of Oceanography) are international collaborators of the project. The British participation in this cruise was made possible thanks to Joint Project Agreement recently signed between the Bedford Institute of Oceanography (BIO) and NERC.

RAPID-WAVE aims at investigating how signals associated with changes in the Atlantic meridional overturning circulation propagate along the Atlantic deep western boundary current. As part of the project, two cruises took place in 2004. In the first one (27 April-6 May 2004, RV Oceanus, OC 401, WHOI), a line of 6 Bottom Pressure Recorders (BPR) was deployed in an operation area approximately located at 36.5 N 67.5 W. In the second one (5-24 August 2004, RRS Charles Darwin, CD160), two additional lines of 6 BPRs and 5 CTD moorings each were deployed on the continental shelf break approximately south of St. John's and southeast of Halifax, respectively.
The third cruise of this RAPID project took place in April 2006 with the recovery and redeployment of BPRs along the WHOI line (5-15 April 2006, RV Oceanus, OC 421, WHOI). Only two of the six BPRs originally deployed on this line could be recovered. However, these two instruments were redeployed together with three new ones.
The fourth RAPID-WAVE cruise was D308, whose aim was to recover and redeploy the BPRs and moorings deployed in 2004 along the St. John's and Halifax lines. In conjunction with the recovery/redeployment operations, CTD casts were planned to be carried out and to include helium, tritium and oxygen sampling (for calibration of the CTD oxygen sensor). Measurement of tritium-helium ratios provides estimates of ventilation age up to about 20 year and is therefore very useful for inferring timescales of water-mass age and tracer transport by the Atlantic deep western boundary current. The cruise encountered mixed success as regards the recovery of instruments: only 50% of the BPRs and 20% of the moorings could be retrieved. All planned CTD casts and sampling operations were completed and all recovered instruments were redeployed.

The RAPID-WAVE objectives during Hud2007045 were to recover and redeploy the two CTD-CM-BPR moorings deployed during the 2006 D308 cruise and also to recover and redeploy two of the six BPRs of the Halifax line. All objectives were achieved without significant problems, a success which is largely due to the support received by the RAPID-WAVE team from BIO technicians and scientists as well as the Hudson's officers and crew.